Fig. 6. (A) Relative permeabilities with reference to Na⁺ (defined as 1) for K⁺, NMDG⁺, choline⁺, Cl^- and Br^- in C7-vec, C7-cld2, and C11-vec, as derived from measurement of biionic (Na⁺/K⁺, Na⁺/NMDG⁺, Na⁺/choline⁺) and dilution potentials (Na⁺/Cl^-, Na⁺/Br^-, n=6). Lower values compared with C7-vec were detected for NMDG⁺, choline⁺, Cl^- and Br^- in both clones C7-cld-2 and C11-vec (P<0.001). (B) Permeabilities for mannitol and lactulose were calculated from ³H-mannitol and ³H-lactulose fluxes and were not significantly different in monolayers of MDCK clone C7 without or with transfection with claudin-2 cDNA (n=4 and 6, respectively), although they were lower than in clone C11-vec (n=4 and 6, respectively, P<0.05). (C) Partial ion conductivities calculated for Na⁺, K⁺ and Cl^- in C7-vec, C7-cld-2 and C11-vec (n=6). Because Na⁺ and K⁺ were almost equally permeable but Na⁺ is 26-fold higher concentrated than K⁺, the contribution of Na⁺ to overall conductivity is about 25-fold of that of K⁺.

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